The initial stages of an offensive strike against Islamic State forces in Mosul saw success Monday, as forces reclaimed villages and made their way closer to the occupied city.

The strike intends to recapture the city that has become the Islamic State’s main stronghold in northern Iraq, but also will serve as a test of President Obama’s effort to defeat extremists without putting American forces on the ground. Instead, US forces are supporting a collaborative effort by the Kurdish Peshmerga, Sunni tribal fighters, and the Iraqi military to retake the city.

By the beginning of the second day of the battle, Kurdish fighters had seized nine villages to recapture 200 km of land in just 24 hours.

"Early indications are that Iraqi forces have met their objectives so far, and that they are ahead of schedule for this first day,” Pentagon spokesman Peter Cook told reporters during a breifing in Washington. "This is going according to the Iraqi plan – but again, it's early, and the enemy gets a vote here. We will see whether [IS] stands and fights."

While the United States has not deployed any forces on the ground, US air support, artillery, intelligence, advisers, and forward air controllers are assisting the 30,000 Iraqi personnel involved in the fight, and they remain “in harm’s way,” Mr. Cook said.

Still, the plan puts American forces at a lower risk than a US-led offensive would.

“It’s much more sustainable in terms of blood and treasure than obviously having our forces have to do it,” David Petraeus, the former Army general who commanded US and coalition forces in Iraq in 2007-08 and also served as Mr. Obama’s CIA director, said Sunday on ABC’s “This Week.”

Officials estimate that between 4,000 and 8,000 Islamic State fighters remain in Mosul after capturing the city of 1.5 million people two years ago.

If Iraqi and Kurdish forces successfully retake Mosul, tension is likely to remain between the nation’s Sunni, Shiite, and Kuridish populations. Now allied against a common enemy, these groups could clash again in violent ways following a successful military campaign.

“I think there’s a strong possibility that a lot of the political grievances actually get accentuated,” Seth Jones, a defense and security expert at the RAND Corp, told the Associated Press Friday.

By letting local forces have control of the push, the Obama administration hopes to defeat ISIS ideologically, rather than just with military force. A US-led effort likely would have depleted IS forces in Mosul sooner, but officials feared it would also fail to eradicate the extremist ideology in the ways that local leadership may be able to do.

“If we were to take control of this campaign, I mean literally seize control of the campaign, then there’s no doubt in my mind we would probably defeat ISIL on, let’s say, a faster timeline,” Gen. Martin Dempsey, a top military advisor to Obama at the time of the decision, told the Associated Press. “Maybe ISIL goes away, maybe they’re defeated militarily, and two years from now another group with another name and another ideology ... will just be back.”